EPS Manufacturing

By:  Dennis Smith – Packaging Specialist

EPS (Expandable Polystyrene) Foam that is manufactured from EPS Resin is a closed-cell, lightweight and rigid material used in a range of applications from specialized packaging to cold-chain shipment of food, pharmaceuticals, wine, and many other temperature sensitive products as well as numerous architectural applications.

Manufacturing EPS resin into EPS foam is accomplished in three main stages: Pre-expansion, Aging and Molding.

  1. Pre-Expansion:

In pre-expansion, EPS resin is expanded through a steam-supplied pre-expander to varying levels to meet a specific density requirement. A blowing-agent (Pentane) expands the individual beads and the larger the beads expand, the lower the beads decrease in density.

The pre-expanded beads are then sometimes sent through a dryer to remove moisture and then transported to storage bags to age for a period of time.

2. Aging:

During the aging process, the pre-expanded beads are allowed to reach equilibrium with atmospheric pressure. Any remaining moisture is then evaporated and excess residual blowing agent evaporates.


Aged, pre-expanded beads are then transported to molding equipment to form billets of various dimensions or to a custom tool designed to meet a wide variety of specific customer product requirements and applications.

This is done by filling the interior of the tool or molding equipment with pre-expanded beads of the required density specified for a particular application. Heat is then applied to the pre-expanded bead by the introduction of steam. The pre-expanded beads then expand to the geometry of the molding machine or the custom tool. The molded billet/part is cooled and the ‘finished part’ is then ejected from the mold.

A ‘molded billet’ may then be hot-wire cut to a desired dimension and the custom-molded part may have a post-expansion step/steps to achieve a ‘finished product’.

ACH has nine plants throughout the United States. One plant is standalone; Kansas City, which makes both loose-Fill packaging peanuts and block-style EPS for fabricated packaging and insulation.  The remaining eight plants manufacture billets to varying densities and  EPS for architectural applications. Five of our plants also manufacture custom molded packaging products.

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